dialan

Trying to find out what has made my budgies sick. I have lost 2 female lutino budgies age between 12months and 20months. I had one older female budgie about 4 years old she got sick but has pulled through. They are in an out door aviary. They were fine one day, then the next day there poo is stuck to the vent (pastey), they are fluffed up and dead within 24hrs. There aviary is regularly cleaned and is a concrete slab. They are regularly wormed. Any suggestions what could be causing the problem.